POTENTIAL EFFECTS OF CLIMATE CHANGE ON PARTICLE COAGULATION EFFICIENCY IN THE OCEAN

Marine particle formation and the subsequent export of organic carbon from the pelagic zone is an important mechanism for sequestering CO2. We studied the effect of increased CO2 concentrations and temperature on the coagulation efficiency of phytoplankton, a factor important for modeling aggregate formation. Dissolved and colloidal exudates derived from phytoplankton during blooms are enriched in acidic sugars and have recently been shown to be precursors for abiotically-formed gel particles operationally classified as transparent exopolymer particles (TEP). It has been suggested that TEP enhances aggregation by increasing effective particle size and collision frequency of particles, and also by serving as organic glue between cells. TEP abundance, dissolved and colloidal neutral and acidic sugar composition, and cellular abundances were measured for diatoms grown in mesocosms at elevated temperatures and for coccolithophores grown in chemostats under different temperatures and pCO2 concentrations. Coagulation efficiency of cells undergoing collisions by shear was determined experimentally using horizontal Couette devices. Here we report our findings and discuss their implications for marine particle dynamics and the marine carbon cycle in the future

Importance of Calcareous Shells in Aggregate Formation and Particle Decomposition for the Coccolithophorid Emiliania Huxleyi

Stand from May ABCDEFGHIJKLMNOPQRSTUVWXYZ Saline outflow from the Arctic Ocean its contribution the deep waters the Greenland Norwegian and Iceland Seas Journal Geophysical Research Aagaard Fahrbach Meincke Swift Structure and geological processes The expedition ARKTIS XVII the Research Vessel POLARSTERN Fahrbach Reports Polar and Marine Research Alfred Wegener Institute for Polar and Marine Research Bremerhaven Aahke Hohmann Kierdorf Matthiessen Vernaleken Parameterisierung atmosph rischer Grenzschichtprozesse einem regionalen Klimamodell der Arktis Reports Polar Research Alfred Wegener Institute for Polar and Marine Research Bremerhaven Abegg Parameterisierung atmosph rischer Grenzschichtprozesse einem regionalen Klimamodell der Arktis Parameterisation atmospheric boundary layer processes regional climate model the Arctic Reports Polar Research Alfred Wegener Institute for Polar and Marine Research Bremerhaven Abegg Influence planetary boundary layer parameterization Arctic climate simulations ACSYS Conference Polar Processes and Global Climate WMO ICSU IOC World Climate Research Programme WCPR Proceedings Abegg Dethloff Rinke Romanov Untersuchungen zur Parameterisierung der planetaren Grenzschicht der Arktis Ann Meteorol Abegg Dethloff Rinke Romanov Influence planetary boundary layer parameterization Arctic climate simulations Proc the ACSYS conference Polar processes and global climate Rosario Resort Nov WMO Abegg Dethloff Rinke Hebestadt Romanov Fabric gas hydrate sedim

Investigating the effect of ballasting by CaCO3 in Emiliania huxleyi: II. Decomposition of particulate organic matter

To investigate the role of ballasting by biogenic minerals in the export of organic matter in the ocean, a laboratory experiment was conducted comparing aggregate formation and settling velocity of non-calcifying and calcifying strains of the coccolithophore Emiliania huxleyi. Experiments were conducted by making aggregates using a roller table and following aggregate properties during incubation for a period of 40 days. Size, shape, and settling velocities of aggregates were described by image analysis of video pictures recorded during the roller tank incubation. Our results show that biogenic calcite has a strong effect on the formation rate and abundance of aggregates and on aggregate properties such as size, excess density, porosity, and settling velocity. Aggregates of calcifying cells (AGGCAL) formed faster, were smaller and had higher settling velocities, excess densities, and mass than those of non-calcifying cells (AGGNCAL). AGGCAL showed no loss during the duration of the experiment, whereas AGGNCAL decreased in size after 1 month of incubation. Potential mechanisms that can explain the different patterns in aggregate formation are discussed. Comparison of settling velocities of AGGCAL and AGGNCAL with aggregates formed by diatoms furthermore indicated that the ballast effect of calcite is greater than that of opal. Together these results help to better understand why calcite is of major importance for organic matter fluxes to the deep ocean